Despite the wide use and acceptance of penicillins and cephalosporins, beta-lactam antibiotics, in combating bacterial infections, there are certain members within the group that are not active against resistant microorganisms because of the organism's ability to produce a beta-lactamase enzyme which reacts with beta-lactam antibiotic to produce products devoid of antibacterial activity. However, certain substances have the ability to inhibit beta-lactamases, and when used in combination with a penicillin or cephalosporin can increase or enhance the antibacterial effectiveness of the antibiotic against certain beta-lactamase producing microorganisms.
West German Offenlegungsschrift No. 2,824,535 published Dec. 14, 1978 teaches that penicillanic acid sulfone is such an effective beta-lactamase inhibitor. In addition, it is taught in said application that certain esters of penicillanic acid sulfone are readily hydrolyzable in vivo giving high blood levels of this beta-lactamase inhibitor. Further, U.K. patent application No. 2,044,255 and U.S. Pat. No. 4,244,951 also teaches that halomethyl esters of penicillanic acid sulfone can be coupled through the carboxy group of an antibacterial penicillin to give compounds with readily hydrolyzable esters which degrade in vivo into anti-bacterial penicillins and the beta-lactamase inhibitor penicillanic acid sulfone.
U.K. patent application No. 2,044,255 further teaches that the intermediate chloromethyl penicillanate sulfone can be prepared by coupling the potassium salt of penicillanic acid sulfone with chloroiodomethane in the presence of a catalytic amount of tetrabutylammonium sulfate. In addition it is reported that the tetrabutylammonium salts of certain penicillanic antibacterial agents can be coupled with alpha-haloalkyl penicillanate sulfones to give compounds with readily hydrolyzable esters which degrade in vivo into antibacterial penicillins and penicillanic acid sulfone.